High-quality strong beverages are produced from spirits (brandy, calvados and the like spirits) by of a long maturation in oak barrels (up to 10-15 years and longer) through the walls of which barrels oxygen diffuses and interacts with the alcohol.
During such maturation green alcohols are enriched with wood components (tanning substances), and acquire a characteristic colour, as well as a specific bouquet and taste. The quality of the resulting strong beverage is in a direct relationship to the duration of its maturation (cf. USSR Inventor's Certificate No. 87105).
However, this process for maturing strong beverages is accompanied by inevitable and considerable losses of the starting spirit through evaporation thereof out of pores of an oak barrel (up to 50%), since the process technology does not provide for an outside coating of barrels with sealing materials. Moreover, a long-time maturation of spirits in oak barrels causes a considerable consumption and an inefficient utilization of a high-quality aged oak stave which is a rarely-available item in the wine technology.
In order to avoid losses of spirits from evaporation and to reduce the consumption of oak stave, a tank process for maturing strong beverages has been developed and is now employed on a wide scale (cf. "Basic Rules in the Production of Cognacs"; USSR Ministry of Food Industry, 1978, p. 12-16).
The process involves a special preliminary preconditioning of the oak stave. One of embodiments of this preconditioning resides in that the stave is soaked in alkali solutions at an elevated temperature for a period of several days. Then the soaked stave is placed in a tank, brandy spirit and the latter is matured in the presence of the stave for 3 to 5 years with an intermittent saturation with oxygen. The resulting finished product is separated from the stave. In order to recover the residual spirit from the spent stave, the latter is subjected to a special treatment; for example, it is covered with water, kept for 12 days and the thus-obtained aqueo-alcoholic mixture is distilled. The process is rather time-consuming, the degree of recovery of the residual spirit from the used stave is not high and its quality is but unsatisfactory. Furthermore, the recovery of the residual alcohol from the spent stave is a labour-consuming process as well.
In order to reduce the duration of the ageing process and to improve quality of the brandy spirit, the tank process involves a preliminary (prior to maturation) enrichment of green brandy spirits by wood components (phenolic substances) by conventional methods. Such a method involves heat-treatment of the solution in an enameled vessel with oak stave at a temperature within the range of from 35.degree. to 45.degree. C. for 30 to 50 days.
However, this mode of preliminary enrichment of a brandy spirit with polyphenolic substances, as with other methods, is of a low efficiency, since neither of them enables a considerable reduction of the process duration of maturation of strong beverages.
Known in the art is another process for maturing strong beverages comprising a preliminary (prior to maturation) wetting of oak stave by hydrogen peroxide, followed by activation by a heat-treatment in an oxygen-containing medium under a pressure of 0.314 to 0.490 MPa at a tempeature of from 120.degree. to 150.degree. C. for 12 to 24 hours (cf. USSR Inventor's Certificate No. 798170). Then the activated wooden stave is air-dried and introduced into a brandy spirit which is aged in the presence of the stave for 3 to 5 years. Thereafter, the beverage is separated from the stave. The heat-treatment stage of this process is of rather long duration, deactivation of the antioxidizing ability of polyphenols of the oak wood occurs predominantly on the surface thereof, since deactivation of the antioxidizing ability of inaccessible polyphenols in the inner bulk of the wood as achieved by this process is inefficient. The process does not make it possible to obtain a product with high organoleptic characteristics, neither does it allow the possibility of activation of the used oak stave and a repeated use thereof.
Therefore, the prior art methods do not make it possible to substantially reduce the duration of the process of maturation of strong beverages simultaneously with ensuring high organoleptic properties of the finished product, or to repeatedly utilize the used stave.